Gnomes experiment with all manner of mechanical devices. Gnomes with this racial trait gain a +1 bonus on Disable Device and Knowledge (engineering) checks. They are treated as proficient with any weapon they have personally crafted. This racial trait replaces defensive training and hatred.

trait apply to:
a) weapons bought on start of game
b) weapons created temporary by some spell, for example Shadow Weapon

I am looking at some cheap ways to give my Indiana Jones version of gnome illusionist a free whip proficiency.

As far as I know the pfs guide to play on pg. 8 states under the feat section that except for specific examples in additional resources that no crafting or creating of mundane items is legal. I believe the only legal ones are for gunsmithing and craft alchemy.

I'm considering a gnome with the master tinker alternate racial trait for PFS and was wondering the same thing. Is there an official answer to this, or is the proficiency aspect of this trait just ignored in PFS play?

the trait is pfs legal, but afaik it would never apply to anything, because you can't really "craft" anything to gain proficiency with. A bonded item is a stretch, since you're crafting (magic item) crafting on it, you still haven't made the original item. For gunslingers it would be pointless since they're already proficient in the firearms.